Thrust bearing made of synthetic resin

ABSTRACT

A thrust bearing made of synthetic resin assembled into a strut-thrust type suspension for use in four wheel cars, comprising a casing made of synthetic resin and a bearing body made of synthetic resin, the bearing body being fitted rotatably to the casing by snap-fitting a hook portion of a suspended portion with an engaging portion of a protruded portion, the suspended portion being formed integrally with an outer circumferential edge of the casing, the protruded portion being formed integrally with an outer circumferential edge of the bearing body.

The present invention concerns a thrust bearing made of synthetic resin,particularly, it relates to a thrust bearing made of synthetic resinassembled into a strut-thrust type suspension (MacPherson type) for usein four wheel cars.

Generally, a strut-thrust type suspension is mainly used for the frontwheels of four wheel cars in which coil springs are combined with astrut assembly incorporating an oil pressure type shock absorber in anouter cylinder integrated with a main shaft. The suspension describedabove includes such a type in which a piston rod of a strut assembly isrotated when the assembly is rotated together with coil springs by asteering operation and another type in which the piston rod is notrotated. In both of the types, a thrust bearing is required between themounting member of the assembly to a vehicle body and the upper springseat of the coil assembly for allowing the smooth rotation of the strutassembly.

Roller bearings using balls or needles, or sliding type thrust bearingsmade of synthetic resin have been employed so far in these portions.

A dust seal made of an elastic rubber member is mounted at the outercircumference of the sliding surface for the thrust bearing made ofsynthetic resin for preventing the intrusion of dust or the like fromthe outside of the bearing to the sliding surface.

In the prior art described above, since a dust seal is disposed to theouter circumference of the sliding surface for the thrust bearing, thereis a drawback that the sliding frictional force is increased uponsteering operation thereby requiring great steering force.

The present invention is achieved in order to overcome the foregoingdrawback in the prior art and it is an object of the invention to obtaina thrust bearing made of synthetic resin capable of preventing theintrusion of dust or the like without using dust seals made of elasticrubber members and thereby preventing increase of the steering powerupon steering operation.

The foregoing object can be attained by the following constitutions inaccordance with the present invention, that is:

a first thrust bearing made of synthetic resin comprising a casing madeof synthetic resin and a bearing body made of synthetic resin fitted tothe casing, the casing including a cylindrical portion having apenetration aperture being along a longitudinal direction thereof, alarge width collar portion formed integrally with an outercircumferential surface of the cylindrical portion, an annular protrudedportion formed integrally with an outer circumferential edge of thelarge width collar portion and an engaging portion formed to an outercircumferential surface of the protruded portion, the bearing bodyincluding a cylindrical bearing portion, an inner collar portion formedintegrally with an upper end of an inner circumferential surface of thebearing portion, an outer collar portion formed integrally with an upperend of an outer circumferential surface of the bearing portion, anannular suspended portion formed integrally with a circumferential edgeof the outer collar portion and an engaging hook portion formed at alower end of the suspended portion, the bearing body being fittedrotatably to the casing by snap-fitting the hook portion of thesuspended portion with the engaging portion of the protruded portionsuch that a lower surface of the bearing portion is slidably abuttedagainst an upper surface of the large width collar portion of thecasing, whereby a tight seal is formed in the snap-fit portion;

a second thrust bearing made of synthetic resin comprising a casing madeof synthetic resin and a bearing body made of synthetic resin fitted tothe casing, the casing including a cylindrical portion having apenetration aperture being along a longitudinal direction thereof, alarge width collar portion formed integrally with an outercircumferential surface of the cylindrical portion, an annular protrudedportion formed integrally with an outer circumferential edge of thelarge width collar portion, an annular protruded portion formedintegrally with an outer circumferential edge of the large width collarportion, an engaging portion formed to an outer circumferential surfaceof the annular protruded portion and an annular lower lip portion formedcoaxially with the penetration aperture at an upper surface of the largewidth collar portion and defining an annular groove in cooperation withone end of the cylindrical portion, the bearing body including acylindrical bearing portion, an inner collar portion formed integrallywith an upper end of an inner circumferential surface of the bearingportion, an outer collar portion formed integrally with an upper end ofan outer circumferential surface of the bearing portion, an annularsuspended portion formed integrally with a circumferential edge of theouter collar portion, a engaging hook portion formed at a lower end ofthe suspended portion and an annular upper lip portion formed coaxiallywith the bearing portion at a lower surface of the outer collar portion,the bearing body being fitted rotatably to the casing by snap-fittingthe hook portion of the suspended portion with the engaging portion ofthe protruded portion such that a lower surface of the bearing portionis slidably abutted against a bottom surface of the groove and an end ofthe upper lip portion is overlapped radially with the lower lip portion,whereby tight seals are formed in the snap-fit portion and in the upperand lower lip portions respectively;

a third thrust bearing made of synthetic resin comprising a casing madeof synthetic resin and a bearing body made of synthetic resin fitted tothe casing, the casing including a cylindrical portion having apenetration aperture being along a longitudinal direction thereof, anannular first lower lip portion disposed to an upper end surface of thecylindrical portion and having an aperture of a diameter enlarging witha step from the penetration aperture, a large width collar portionformed integrally with an outer circumferential surface of thecylindrical portion, an annular protruded portion formed integrally withan outer circumferential edge of the large width collar portion, anengaging portion formed to an circumferential surface of the protrudedportion and an annular second lower lip portion formed coaxially withthe penetration aperture to an upper surface of the large width collarportion and defining an annular groove in cooperation with the firstlower lip portion, the bearing body including a cylindrical bearingportion, an inner collar portion formed integrally with an upper end ofan inner circumferential surface of the bearing portion, an annularfirst upper lip portion formed integrally with an inner circumferentialedge of the inner collar portion and extended downwardly, an outercollar portion formed integrally with an outer circumferential surfaceof the bearing portion, an annular suspended portion formed integrallywith an circumferential edge of the outer collar portion, an engaginghook portion formed at a lower end of the suspended portion and a secondannular upper lip portion formed coaxially with the bearing portion to alower surface of the outer collar portion, the bearing body being fittedrotatably to the casing by snap-fitting the hook portion of thesuspended portion with the engaging portion of the protruded portionsuch that a lower surface of the bearing portion is slidably abuttedagainst a bottom surface of the groove and ends of the first and secondupper lip portions are overlapped radially with ends of the first andsecond lower lip portions respectively, whereby tight seals are formedin the snap-fit portion, in the first upper and lower lip portions andthe second upper and lower lip portions respectively;

a fourth thrust bearing made of synthetic resin comprising a casing madeof synthetic resin and a bearing body made of synthetic resin fitted tothe casing, the casing including a cylindrical portion having apenetration aperture being along a longitudinal direction thereof, alarge width collar portion formed integrally with an outercircumferential surface of the cylindrical portion, an annular protrudedportion formed integrally with an outer circumferential edge of thelarge width collar portion, an engaging step formed to an outercircumferential surface of the annular protruded portion, asubstantially cylindrical first bearing portion formed integrally withan upper surface of the large width collar portion and an annular ridgeportion formed at an inner circumferential edge of the first bearingportion in continuous with the inner circumferential edge and protrudedfrom an end face of the first bearing portion, the bearing bodyincluding a disk-like portion having a circular aperture at a centralportion thereof, a cylindrical second bearing portion formed to a lowersurface of the disk-like portion, an annular inner protruded portionspaced apart from an inner circumferential surface of the second bearingportion by an annular first groove, protruded at a leading end thereoffrom an end face of the second bearing portion and formed in continuouswith the circular aperture, an annular outer protruded portion spacedapart from an outer circumferential surface of the second bearingportion by an annular second groove and protruded at a leading endthereof from the end face of the second bearing portion and an annularsuspended portion formed at an outer circumferential edge of thedisk-like portion and having an engaging hook portion at a leading endthereof, the bearing body being fitted rotatably to the casing bysnap-fitting the hook portion of the suspended portion to the engagingstep of the protruded portion such that the end face of the secondbearing portion is abutted slidably against an end face of the firstbearing portion and the leading ends of the inner and outer protrudedportions are protruded from the end face of the first bearing portion;

a fifth thrust bearing made of synthetic resin comprising a lower casingmade of synthetic resin, an upper casing made of synthetic resin and abearing piece made of synthetic resin disposed within the upper andlower casings, the lower casing including a cylindrical portion having apenetration aperture being along a longitudinal direction thereof, alarge width collar portion formed integrally with an outercircumferential surface of the cylindrical portion, an annular protrudedportion formed integrally with an outer circumferential edge of thelarge width collar portion and an engaging portion formed to an outercircumferential surface of the protruded portion, the upper casingincluding a disk-like flat portion, a circular aperture formed at acenter of the disk-like portion, an annular suspended portion formedintegrally with an outer circumferential edge of the disk-like portionand an engaging hook portion formed to a lower end of the suspendedportion, the bearing piece comprising an annular plate having an innerdiameter greater than an outer diameter of the cylindrical portion andan outer diameter smaller than an inner diameter of the protrudedportion, the upper casing being fitted rotatably to the lower casing bysnap-fitting the hook portion of the suspended portion with the engagingportion of the protruded portion such that an upper surface of thebearing piece is slidably abutted against a lower surface of the flatportion and a lower surface of the bearing piece is slidably abuttedagainst an upper surface of the large width collar portion;

a sixth thrust bearing made of synthetic resin comprising a lower casingmade of synthetic resin, an upper casing made of synthetic resin and abearing piece made of synthetic resin disposed within the upper andlower casings, the lower casing including a cylindrical portion having apenetration aperture being along a longitudinal direction thereof, alarge width collar portion formed integrally with an outercircumferential surface of the bearing portion, an annular protrudedportion formed integrally with an outer circumferential edge of thelarge width collar portion, an engaging portion formed to an outercircumferential surface of the protruded portion and an annular lowerlip portion formed coaxially with the penetration aperture at an uppersurface of the large width collar portion and defining an annular groovein cooperation with one end of the cylindrical portion, the upper casingincluding a disk-like flat portion, a circular aperture formed at acenter of the disk-like portion, an annular suspended portion formedintegrally with an outer circumferential edge of the disk-like portion,an engaging hook portion formed at a lower end of the suspended portionand an annular upper lip portion formed coaxially with the circularaperture at a lower surface of the disk-like portion, the bearing piececomprising an annular plate having an inner diameter greater than anouter diameter of the cylindrical portion and an outer diameter smallerthan an inner diameter of the lower lip portion, the upper casing beingfitted rotatably to the lower casing by snap-fitting the hook portion ofthe suspended portion with the engaging portion of the protruded portionsuch that an upper surface of the bearing piece is slidably abuttedagainst a lower surface of the disk-like portion and a lower surface ofthe bearing piece is slidably abutted against a bottom surface of thegroove whereby tight seals are formed in the snap-fit portion and in theupper and lower lip portions; and

a seventh thrust bearing made of synthetic resin comprising a lowercasing made of synthetic resin, an upper casing made of synthetic resinand a bearing piece made of synthetic resin disposed within the upperand lower casings, the lower casing including a cylindrical portionhaving a penetration aperture being along a longitudinal directionthereof, an annular first lower lip portion disposed to an upper endface of the cylindrical portion and having an aperture of a diameterenlarging with a step from the penetration aperture, a large widthcollar portion formed integrally with an outer circumferential surfaceof the cylindrical portion, an annular protruded portion formedintegrally with an outer circumferential edge of the large width collarportion, an engaging portion formed to an outer circumferential surfaceof the protruded portion, an annular second lower lip portion formedcoaxially with the penetration aperture at an upper surface of the largewidth collar portion and defining an annular groove in corporation withthe first lower lip portion, the upper casing including a disc-like flatportion, a circular aperture formed at a center of the disk-likeportion, an annular first upper lip portion formed integrally with aninner circumferential edge of the disk-like portion and extendeddownwardly, an annular suspended portion formed integrally with an outercircumferential edge of the disk-like portion, an engaging hook portionformed at a lower end of the suspended portion and an annular secondupper lip portion formed coaxially with the circular aperture to a lowersurface of the flat portion, the bearing piece comprising an annularplate having an inner diameter greater than an outer diameter of thefirst lower lip portion and an outer diameter smaller than an innerdiameter of the second lower lip portion, the upper casing being fittedrotatably to the lower casing by snap-fitting the hook portion of thesuspended portion with the engaging portion of the protruded portionsuch that an upper surface of the bearing piece is slidably abuttedagainst a lower surface of the flat portion and ends of the first andsecond upper lip portions are overlapped radially with ends of the firstand second lower lip portions respectively and a lower surface of thebearing piece is slidably abutted against a bottom surface of thegroove, whereby tight seals are formed in the snap-fit portion, in thefirst upper and lower lip portions and in the second upper and lower lipportions respectively.

According to the first thrust bearing of the present invention,advantageous effects as described below can be obtained. Since tightseals are formed by the labyrinth effect in the snap-fit portion betweenthe engaging portion of the casing and the engaging hook portion of thebearing body, intrusion of dust or the like to the sliding face of thebearing can be prevented. In addition, since dust seals made of elasticrubber member used so far can be deleted, undesirable increase in thesteering force upon steering operation due to the dust seals can beavoided and smooth steering operation is possible for a long period oftime.

Moreover, since the casing and the bearing body can be engaged bysnap-fitting, the assembly work can be conducted extremely easily.

According to the second thrust bearing of the present invention,advantageous effects as described below can be obtained. Since doubletight seals are formed by the labyrinth effect in the snap-fit portionbetween the engaging portion of the casing and the engaging hook portionof the bearing body, and in the overlapped portion between the upper andlower lip portions respectively intrusion of dust or the like to thesliding face of the bearing can be prevented. In addition, since dustseals made of elastic rubber member used so far can be deleted,undesired increase in the steering force upon steering operation due tothe dust seals can be avoided and smooth steering operation is possiblefor a long period of time.

Further, since the casing and the bearing body can be engaged bysnap-fitting, the assembly work can be conducted extremely easily.

According to the third thrust bearing of the present invention,advantageous effects as described below can be obtained. Since tripletight seals are formed by the labyrinth effect in the snap-fit portionbetween the engaging portion of the casing and the engaging hook portionof the bearing body and in the overlapped portions between the firstupper and lower lip portions and between the second upper and lower lipportions respectively, intrusion of dust or the like from the inner andouter circumferential surfaces of the bearing to the sliding face of thebearing can be prevented. Moreover, since dust seals made of elasticrubber member used so far can be deleted, undesirable increase in thesteering force upon steering operation due to the dust seals can beavoided and smooth steering operation is possible for a long period oftime.

Further, since the casing and the bearing body can be engaged bysnap-fitting, the assembly work can be conducted extremely easily.

According to the fourth thrust bearing of the present invention,advantageous effects as described below can be obtained. Since thesliding contact face of the bearing is formed at a position higher thanthe upper surface of the large width collar portion of the casing andthe inner and outer protruded portions of the bearing body are protrudedfrom the sliding face, the sliding face can be protected against theintrusion of dust or the like from the outside by the labyrinth effectdue to the tight seal formed to the inner and outer circumferentialedges of the sliding face and the tight seal formed in the snap-fitportion between the bearing body and the casing. Further, since thecasing and the bearing body can be fitted by a snap-fitting, theassembly work can be conducted extremely easily.

According to the fifth thrust bearing of the present invention,advantageous effects as described below can be obtained. Since tightseals are formed by the labyrinth effect in the snap-fit portion betweenthe engaging portion of the upper casing and the engaging hook portionof the lower casing, intrusion of dust or the like to the sliding faceof the bearing can be prevented. In addition, since dust seals made ofelastic rubber member used so far can be deleted, undesirable increasein the steering force upon steering operation due to the dust seals canbe avoided and smooth steering operation is possible for a long periodof time.

Further, since the upper casing and the lower casing can be engaged bysnap-fitting, the assembly work can be conducted extremely easily.

According to the sixth thrust bearing of the present invention,advantageous effects as described below can be obtained. Since doubletight seals are formed by the labyrinth effect in the snap-fit portionbetween the engaging portion of the upper casing and the engaging hookportion of the lower casing and in the overlapped portion between theupper and lower lip portions respectively, intrusion of dust or the liketo the sliding face of the bearing can be prevented. In addition, sincedust seals made of elastic rubber member used so far can be deleted,undesirable increase in the steering force upon steering operation dueto the dust seals can be avoided and smooth steering operation ispossible for a long period of time.

Further, since the upper casing and lower casing can be engaged bysnap-fitting, the assembly work can be conducted extremely easily.

According to the seventh thrust bearing of the present invention,advantageous effects as described below can be obtained. Since tripletight seals are formed by the labyrinth effect in the snap-fit portionbetween the engaging portion of the upper casing and the engaging hookportion of the lower casing and in the overlapped portion between thefirst upper and lower lip portions and between the second upper andlower lip portions respectively, intrusion of dust or the like from theinner and outer circumferential surfaces of the bearing to the slidingface of the bearing can be prevented. In addition, since dust seals madeof elastic rubber member used so far can be deleted, undesirableincrease in the steering force upon steering operation due to the dustseals can be avoided and smooth steering operation is possible for along period of time.

Further, since the upper casing and lower casing can be engaged bysnap-fitting, the assembly work can be conducted extremely easily.

In the constitution of the thrust bearing according to the presentinvention as described above, it is necessary that the synthetic resinconstituting the casing, the upper casing and the lower casing isexcellent in mechanical properties such as abrasion resistance, impactshock resistance and creep resistance. Further, it is particularlypreferred that the bearing body slidably fitted to the casing or thebearing piece disposed within the upper and lower casings has aself-lubricity, and there can be used preferably, for example,polyacetal resin, polyamide resin, polyester resin, such as polybutyleneterephthalate (PBT) and polyolefine resin such as polyethylene andpolypropylene, as well as polycarbonate resin. Similar synthetic resinto that for the bearing body or the bearing piece can be used for thecasing, the upper casing and the lower casing and it is desirable to usea synthetic resin material that exhibits preferable frictioncharacteristics when combined with the synthetic resin used for thebearing body or the bearing piece and shows a relatively high rigidity.

Examples of desirable combination of resins are as shown in the tablebelow.

                  TABLE                                                           ______________________________________                                                   Casing, upper                                                      Bearing body or                                                                          casing or   Friction  Abrasion                                     bearing piece                                                                            lower casing                                                                              coefficient                                                                             amount (mm)                                  ______________________________________                                        polyacetal polyamide   0.05      0.020                                        polyamide  polyacetal  0.04      0.021                                        polyethylene                                                                             polyacetal  0.04      0.038                                        polycarbonate                                                                            polyacetal  0.06      0.050                                        polyacetal PBT         0.07      0.045                                        polyacetal polyacetal  0.06      0.025                                        polyacetal steel       0.11      0.095                                        ______________________________________                                    

In the table, the frictional characteristics show the result obtainedunder the following test conditions.

Test Condition

Thrust load: 350 Kg, angle of swing: ±35°, velocity of swing: 60 cpm,lubrication: silicon grease was coated on the sliding face uponstarting.

The abrasion amount indicates the amount of dimensional change (mm) inthe bearing body or the bearing piece after conducting 1,000,000 cyclesof the test.

If the combination of the synthetic resins for the casing and thebearing body, or the combination of the synthetic resin for the upperand lower casings and the bearing piece is preferably selected asdescribed above, since the sliding face of the bearing is constitutedwith the combination of synthetic resins excellent in theself-lubricity, the friction coefficient is low and stable steeringpower can be maintained for a long period of time.

This invention will be explained more specifically while referring tothe accompanying drawings, by which the foregoing objects as well as theconstitutions of the present invention will become more apparent.

Specific embodiments to be explained hereinafter are given for easyunderstanding of the present invention and various modifications may bepossible by those skilled in the art without departing the scope of thepresent invention as clearly shown in the scope of the claim for patent.

FIG. 1 is a longitudinal cross sectional view of a strut assemblyequipped with a first thrust bearing according to the present invention;

FIG. 2 is a longitudinal cross sectional view of one embodiment of thefirst thrust bearing according to the present invention;

FIG. 3 is a plan view for the bearing body shown in FIG. 2;

FIG. 4 is a bottom view for the bearing body shown in FIG. 2;

FIG. 5 is an enlarged cross sectional view for a part in a snap-fitportion shown in FIG. 2;

FIG. 6 is a longitudinal cross sectional view of one embodiment of thesecond thrust bearing according to the present invention;

FIG. 7 is a plan view for the bearing body shown in FIG. 6;

FIG. 8 is a bottom view for the bearing body shown in FIG. 6;

FIG. 9 is an enlarged cross sectional view for a part in a snap-fitportion shown in FIG. 6;

FIG. 10 is a longitudinal cross sectional view of a strut assemblyequipped with a second thrust bearing according to the presentinvention;

FIG. 11 is a longitudinal cross sectional view of one embodiment of thethird thrust bearing according to the present invention;

FIG. 12 is a plan view for the bearing body shown in FIG. 11;

FIG. 13 is a bottom view for the bearing body shown in FIG. 11;

FIG. 14 is an enlarged cross sectional view for a part in a snap-fitportion shown in FIG. 11;

FIG. 15 is a longitudinal cross sectional view of another embodiment ofthe third thrust bearing according to the present invention;

FIG. 16 is a longitudinal cross sectional view of a strut assemblyequipped with a third thrust bearing according to the present invention;

FIG. 17 is a longitudinal cross sectional view of one embodiment of thefourth thrust bearing according to the present invention;

FIG. 18 is a plan view for the casing shown in FIG. 17;

FIG. 19 is a bottom view for the bearing body shown in FIG. 17;

FIG. 20 is a longitudinal cross sectional view of a strut assemblyequipped with a fourth thrust bearing according to the presentinvention;

FIG. 21 is a longitudinal cross sectional view of one embodiment of thefifth thrust bearing according to the present invention;

FIG. 22 is a plan view for the bearing piece shown in FIG. 21;

FIG. 23 is a longitudinal cross sectional view of a strut assemblyequipped with a fifth thrust bearing according to the present invention;

FIG. 24 is a longitudinal cross sectional view of one embodiment of asixth thrust bearing according to the present invention;

FIG. 25 is a plan view for the bearing piece shown in FIG. 24;

FIG. 26 is a longitudinal cross sectional view of a strut assemblyequipped with a sixth thrust bearing according to the present invention;

FIG. 27 is a longitudinal cross sectional view of one embodiment of aseventh thrust bearing according to the present invention;

FIG. 28 is a plan view for the bearing piece shown in FIG. 27;

FIG. 29 is a longitudinal cross sectional view of another embodiment ofa seventh thrust bearing according to the present invention; and

FIG. 30 is a longitudinal cross sectional view of a strut assemblyequipped with a seventh thrust bearing according to the presentinvention.

In FIG. 1, a thrust assembly A comprises a strut 1 incorporating a shockabsorber and a piston rod 2 inserted at one end into the shock absorberof the strut 1 and protruded at the other end from the shock absorber.The other end of the rod 2 is secured by means of a nut 6 to a mountingmember 5 supported to a vehicle body 4 by way of a mount insulator 3made of elastic rubber material.

A lower spring seat 7 is secured to the outer circumferential surface ofthe strut 1, while an upper spring seat 8 is disposed opposing to theseat 7 and loosely engaged to the outer circumferential surface of therod 2. A coil spring 9 is disposed between the upper and the lower seats7 and 8.

A first thrust bearing 20 made of synthetic resin of the presentinvention is disposed between the flat portion 10 of the seat 8 and themounting members 5, and the thrust bearing 20 comprises a casing 21 madeof synthetic resin and a bearing body 22 made of synthetic resinslidably fitted to the casing 21.

Explanation will be made specifically for one embodiment of a firstthrust bearing according to the present invention referring to FIGS. 2through 4 of the accompanying drawings.

A thrust bearing 20 comprises a casing 21 made of synthetic resin and abearing body 22 made of synthetic resin slidably fitted to the casing21.

The casing 21 includes a cylindrical portion 24 having a penetrationaperture 23 being along a longitudinal direction thereof, a large widthcollar portion 25 formed integrally with an outer circumferentialsurface of the cylindrical portion 24 in a state where one end 24a ofthe cylindrical portion 24 is protruded therefrom, an annular protrudedportion 26 formed integrally with an outer circumferential edge of thecollar portion 25 and an engaging portion 27 formed to an outercircumferential surface of the protruded portion 26. The collar portion25 may be formed at a lower end of the cylindrical portion 24.

The engaging portion 27 consists of a tapered surface portion 27a formedfrom the outer circumferential surface of the protruded portion 26 to anlower surface of the collar portion 25 and a cylindrical surface portion27b in contiguous with the tapered surface portion 27a and reaching thelower surface of the collar 25.

The bearing body 22 made of synthetic resin includes a cylindricalbearing portion 28, an annular inner collar portion 29 formed integrallywith an upper end of an inner circumferential surface of the cylindricalbearing portion 28, an annular outer collar portion 30 formed integrallywith an upper end of the outer circumferential surface of the bearingportion 28, an annular suspended portion 31 formed integrally with ancircumferential edge of the collar portion 30 and an engaging hookportion 32 formed at a lower end of the suspended portion 31. The hookportion 32 consists of a tapered surface portion 32a corresponding tothe tapered surface portion 27a that constitutes the engaging portion 27of the casing 21 and a cylindrical surface portion 32b in continuouswith the tapered surface portion 32a and corresponding to thecylindrical surface portion 27b of the engaging portion 27.

The bearing body 22 is fitted rotatably to the casing 21 by snap-fittingthe hook portion 32 of the suspended portion 31 with the engagingportion 27 of the casing 21, whereby a tight seal is formed by thelabyrinth effect in the snap-fit portion.

A plurality of recesses 33 are formed radially at the upper surface ofthe bearing portion 28 of the bearing body 22, so that the thickness ofthe bearing body 22 is made uniform as much as possible by the recesses33.

A plurality of grooves 34 are formed each at a circumferential pitch atthe lower surface of the bearing portion 28 of the bearing body 22 andeach groove 34 is formed radially from the inner circumferential surfaceto the outer circumferential surface, and the grooves 34 constitute anoil reservoir for grease or like other lubricant. The bearing body 22 isfitted to the casing 21 such that the lower surface of the bearingportion 28 is slidably abutted against the upper surface of the collarportion 25 of the casing 21.

Explanation will be made specifically for one embodiment of the secondthrust bearing according to the present invention referring to FIGS. 6through 9 of the accompanying drawings.

A thrust bearing 20 comprises a casing 21 made of synthetic resin and abearing body 22 made of synthetic resin slidably fitted to the casing21.

The casing 21 includes a cylindrical portion 24 having a penetrationaperture 23 being along a longitudinal direction thereof, a large widthcollar portion 25 formed integrally with an outer circumferentialsurface at the end of the cylindrical portion 24 in a state where oneend 24a of the cylindrical portion 24 is protruded therefrom, an annularprotruded portion 26 formed integrally with an outer circumferentialedge of the collar portion 25, an engaging portion 27 formed to an outercircumferential surface of the protruded portion 26 and an annular lowerlip portion 41 formed coaxially with the penetration aperture 23 at anupper surface of the collar portion 25 and defining an annular groove 40in cooperation with one end 24a of the cylindrical portion 24.

The engaging portion 27 consists of a tapered surface portion 27a formedfrom the outer circumferential surface of the protruded portion 26 to alower surface of the collar portion 25 and a cylindrical surface portion27b in continuous with the tapered surface portion 27a and reaching thelower surface of the collar portion 25.

The bearing body 22 includes a cylindrical bearing portion 28, anannular inner collar portion 29 formed integrally with an upper end ofan inner circumferential surface of the bearing portion 28, an annularouter collar portion 30 formed integrally with the upper end of theouter circumferential surface of the bearing portion 28, an annularsuspended portion 31 formed integrally with the outer circumferentialedge of the collar portion 30, an engaging hook portion 32 formed at alower end of the suspended portion 31 and an annular upper lip portion42 formed coaxially with the bearing portion 28 at a lower surface ofthe collar portion 30 and having an inner diameter larger than an outerdiameter of the annular lower lip portion 41 formed to an upper surfaceof the collar portion 25 of the casing 21.

The hook portion 32 consists of a tapered surface portion 32acorresponding to the tapered surface portion 27a that constitutes theengaging portion 27 of the casing 21 and a cylindrical surface portion32b in continuous with the tapered surface portion 32a and correspondingto the cylindrical surface portion 27b of the engaging portion 27.

The bearing body 22 is fitted rotatably to the casing 21 by snap-fittingthe hook portion 32 of the suspended portion 31 with the engagingportion 27 of the casing 21 and by radially overlapping an end of theupper lip portion 42 with the lower lip portion 41 of the casing 21,whereby tight seals are formed by the labyrinth effect in the snap-fitportion and in the upper and lower lip portions.

A plurality of recesses 33 are formed radially at the upper surface ofthe bearing portion 28 of the bearing body 22, so that the thickness ofthe bearing body 22 is made uniform as much as possible by the recesses33.

A plurality of grooves 34 are formed each at a circumferential pitch atthe lower surface of the bearing portion 28 of the bearing body 22 andeach groove 34 is formed radially from the inner circumferential surfaceto the outer circumferential surface, and the grooves 34 constitute anoil reservoir for grease or like other lubricant. The bearing portion 28of the bearing body 22 is disposed within the groove 40 such that thelower surface of the bearing portion 28 is slidably abutted against thebottom face of the groove 40 of the casing 21.

The sliding face defined with the lower surface of the bearing portion28 of the bearing body 22 and the bottom face of the groove 40 formed tothe casing 21 slidably abutting against the lower surface is protectedagainst the intrusion of dust or the like from the inner circumferentialsurface of the thrust bearing 20 by the labyrinth effect due to thetight seal formed in the snap-fit portion and in the overlapped portionbetween the upper and lower lip portions 42, 41 respectively.

FIG. 10 illustrates an embodiment in which the second thrust bearing 20described above is applied to a strut assembly A.

Specifically, the piston rod 2 of the strut 1 passes through thepenetration aperture 23 in the cylindrical portion 24 of the casing 21,the outer circumferential surface of the cylindrical portion 24 of thecasing 21 is fitted into the aperture of the upper spring seat 8, thelower surface of the collar portion 25 of the casing 21 is abuttedagainst the flat portion 10 of the seat 8 and the upper surface of thebearing body 22 is abutted against the mounting member 5.

Explanation will be made specifically for one embodiment of a thirdthrust bearing according to the present invention referring to FIGS. 11through 14 of the accompanying drawings.

A thrust bearing 20 comprises a casing 21 made of synthetic resin and abearing body 22 made of synthetic resin slidably fitted to the casing21.

The casing 21 includes a cylindrical portion 24 having a penetrationaperture 23 being along a longitudinal direction thereof, an annularfirst lower lip portion 43 disposed to an upper end surface of thecylindrical portion 24 and having an aperture of a diameter enlargingwith a step from the penetration aperture 23, a large width collarportion 25 formed integrally with an outer circumferential surface atthe end of the cylindrical portion 24, an annular protruded portion 26formed integrally with an outer circumferential edge of the collarportion 25, an engaging portion 27 formed to an outer circumferentialsurface of the protruded portion 26 and an annular second lower lipportion 44 coaxially formed with the penetration aperture 23 at an uppersurface of the collar portion 25 and defining an annular groove 40 incooperation with the annular first lower lip portion 43.

The engaging portion 27 consists of a tapered surface portion 27a formedfrom the outer circumferential surface of the protruded portion 26 tothe lower circumferential surface of the collar portion 25 and acylindrical surface portion 27b in continuous with the tapered surfaceportion 27a and reaching the lower surface of the collar portion 25.

The bearing body 22 includes a cylindrical bearing portion 28, anannular inner collar portion 29 formed integrally with an upper end ofan inner circumferential surface of the bearing portion 28, an annularfirst upper lip portion 45 protruding downwardly in continuous with aninner circumferential edge of the collar portion 29 and having an innerdiameter equal with the diameter of the penetration aperture 23 of thecasing 21 and an outer diameter smaller than the inner diameter of thefirst lower lip portion 43, an annular outer collar portion 30 formedintegrally with an upper end at the outer circumferential surface of thebearing portion 28, an annular suspended portion 31 formed integrallywith an outer circumferential edge of the collar portion 30, an engaginghook portion 32 formed at a lower end of the suspended portion 31 and anannular second upper lip portion 46 formed coaxially with the bearingportion 28 to a lower surface of the collar portion 30 and having aninner diameter greater than an outer diameter of the second lower lipportion 44 formed to the upper surface of the collar portion 25 of thecasing 21.

The hook portion 32 consists of a tapered surface portion 32acorresponding to the tapered surface portion 27a that constitutes theengaging portion 27 of the casing 21 and a cylindrical surface portion32b in continuous with the tapered surface portion 32a and correspondingto the cylindrical surface portion 27b of the engaging portion 27.

The bearing body 22 is fitted rotatably to the casing 21 by snap-fittingthe hook portion 32 of the suspended portion 31 with the engagingportion 27 of the casing 21 and by radially overlapping the ends of thefirst and second upper lip portions 45, 46 respectively with the firstand second lower lip portions 43, 44 of the casing 21, whereby tightseals are formed by the labyrinth effect in the snap-fit portion, in thefirst upper and lower lip portions and in the second upper and lower lipportions.

A plurality of recesses 33 are formed radially at the upper surface ofthe bearing portion 28 of the bearing body 22, so that the thickness ofthe bearing body 22 is made uniform as much as possible by the recesses33.

A plurality of grooves 34 are formed each at a circumferential pitch atthe lower surface of the bearing portion 28 of the bearing body 22 andeach groove 34 is formed radially from the inner circumferential surfaceto the outer circumferential surface, and the grooves 34 constitute anoil reservoir for grease or like other lubricant. The bearing portion 28of the bearing body 22 is disposed within the groove 40 such that thelower surface of the bearing portion 28 is slidably abutted against thebottom surface of the groove 40 of the casing 21.

The sliding face defined with the lower surface of the bearing portion28 of the bearing body 22 and the bottom face of the groove 40 isprotected against the intrusion of dust or the like from the inner andthe outer circumferential surfaces of the thrust bearing 20 by thelabyrinth effect due to the tight seals formed in the snap-fit portion,in the overlapped portion between the first upper and lower lip portions45, 43 and the overlapped portion between the second upper and lower lipportions 46, 44 respectively.

FIG. 15 is a longitudinal cross sectional view illustrating anotherembodiment of the third thrust bearing according to the presentinvention.

In this embodiment, an engaging portion 36 is formed to the innercircumferential surface of the first lower lip portion 43 of the casing21, while an engaging hook portion 37 is formed to the outercircumferential surface of the first upper lip portion 45 of the bearingbody 22 in the aforementioned embodiment of the third thrust bearing.Both of the engaging portion 36 and the hook portion 37 are snap-fit toeach other and fitted in a relatively rotatable manner.

FIG. 16 illustrates an embodiment in which one embodiment of the thirdthrust bearing described above is applied to a strut assembly A.

Specifically, the piston rod 2 of the strut 1 passes through thepenetration aperture 23 in the cylindrical portion 24 of the casing 21,the outer circumferential surface of the cylindrical portion 24 of thecasing 21 is fitted into the aperture of the upper spring seat 8, thelower surface of the collar portion 25 of the casing 21 is abuttedagainst the flat portion 10 of the seat 8 and the upper surface of thebearing body 22 is abutted against the mounting member 5.

Explanation will be made specifically for one embodiment of a fourththrust bearing according to the present invention referring to FIGS. 17through 19 of the accompanying drawings.

A thrust bearing 20 comprises a casing 21 made of synthetic resin and abearing body 22 made of synthetic resin slidably fitted to the casing21.

The casing 21 includes a cylindrical portion 24 having a penetrationaperture 23 being along a longitudinal direction thereof, a large widthcollar portion 25 formed integrally with an outer circumferentialsurface at the end of the cylindrical portion 24, an annular protrudedportion 26 formed integrally with an outer circumferential edge of thecollar portion 25, an engaging step 50 formed to the outercircumferential surface of the protruded portion 26, a substantiallycylindrical first bearing portion 51 formed integrally with andprotruded from an upper surface of the collar portion 25 and an annularridge portion 52 formed in continuous with the inner circumferentialedge of the bearing portion 51 and protruded from the end of the bearingportion 51.

The bearing body 22 comprises a disk-like portion 54 having at itscentral portion thereof a circular aperture 53 in communication with thepenetration aperture 23 of the casing 21, a cylindrical second bearingportion 28 formed integrally with the lower surface of the disk-likeportion 54, an annular inner protruded portion 56 spaced apart from aninner circumferential surface of the bearing portion 28 by an annularfirst groove 55, protruded at a leading end thereof from an end face ofthe bearing portion 28 and formed in continuous with the circularaperture 53, an annular outer protruded portion 58 spaced apart from anouter circumferential surface of the bearing portion 28 by a secondannular groove 57 and protruded at a leading end thereof from the endface of the bearing portion 28 and an annular suspended portion 31formed at an outer circumferential edge of the disk-like portion 54 andhaving an engaging hook portion 32 at a leading end thereof.

The bearing body 22 is fitted rotatably to the casing 21 by snap-fittingthe hook portion 32 of the suspended portion 31 with the engaging step50 of the casing 21 such that the end face of the bearing portion 28 isabutted slidably against the end face of the bearing portion 51 at theupper surface of the collar portion 25 and the ends of the inner and theouter protrusions 56, 58 are protruded from the end faces of the bearingportions 28, 51 respectively.

Since the sliding face between the end face of the bearing portion 28and the end face of the bearing portion 51 is formed at a positionhigher than the upper surface 59 of the collar portion 25 by thecombination of the casing 21 and the bearing body 22 and since the innerand outer protrusions 56, 58 of the bearing body 22 are disposed whilebeing protruded from the sliding face, intrusion of dust or the likefrom the outside to the sliding face can be prevented by the labyrintheffect due to the tight seal formed in the inner and outercircumferential edges of the sliding face and the tight seal formed inthe snap-fit portion between the bearing member 22 and the casing 21.

FIG. 20 illustrates an embodiment in which the thrust bearing 20comprising one embodiment of the fourth thrust bearing described aboveis applied to the strut assembly A.

Specifically, the piston rod 2 of the strut 1 passes through thepenetration aperture 23 in the cylindrical portion 24 of the casing 21,the outer circumferential surface of the cylindrical portion 24 of thecasing 21 is fitted into the aperture of the upper spring seat 8, thelower surface of the collar portion 25 of the casing 21 is abuttedagainst the flat portion 10 of the seat 8 and the bearing body 22 isabutted against the mounting member 5.

Explanation will be made specifically for one embodiment of a fifththrust bearing according to the present invention referring to FIGS. 21and 22 of the accompanying drawings.

A thrust bearing 20 comprises a lower casing 60 made of synthetic resin,an upper casing 61 made of synthetic resin and a bearing piece 62 madeof synthetic resin disposed within the upper and lower casings 60, 61.

The lower casing 60 includes a cylindrical portion 64 having apenetration aperture 63 being along a longitudinal direction thereof, alarge width collar portion 65 formed integrally with an outercircumferential surface of the cylindrical portion 64 in a state whereone end 64a of the cylindrical portion 64 is protruded therefrom, anannular protruded portion 66 formed integrally with an outercircumferential edge of the collar portion 65 and an engaging portion 67formed to an outer circumferential surface of the protruded portion 66.

The engaging portion 67 consists of a tapered surface portion 67a formedfrom an outer circumferential surface of the protruded portion 66 to alower surface of the collar portion 65 and a cylindrical surface portion67b in continuous with the tapered surface portion 67a and reaching thelower surface of the collar portion 65.

The casing 61 includes a disk-like flat portion 68, a circular aperture72 formed at a center of the flat portion 68 and having the samediameter as that of the penetration aperture 63, an annular suspendedportion 69 formed integrally with an outer circumferential edge of theflat portion 68 and an engaging hook portion 70 formed at a lower end ofthe suspended portion 69. The hook portion 70 consists of a taperedsurface portion 70a corresponding to the tapered surface portion 67aconstituting the engaging portion 67 of the casing 60 and a cylindricalsurface portion 70b in continuous with the tapered surface portion 70aand corresponding to the cylindrical surface portion 67b of the engagingportion 67.

The casing 61 is fitted rotatably to the casing 60 by snap-fitting thehook portion 70 of the suspended portion 69 with the engaging portion 67of the casing 60, thereby a tight seal is formed by the labyrinth effectin the snap-fit portion.

The bearing piece 62 comprises an annular plate having an inner aperture62a of an inner diameter greater than the outer diameter of thecylindrical portion 64 of the casing 60 and an outer diameter smallerthan the inner diameter of the protruded portion 66 of the casing 60.

A plurality of grooves 62b are formed radially from the inner aperture62a to the outer circumferential surface alternately on both end facesof the bearing piece 62 at a phase difference of 30 degree with eachother in the circumferential direction, and the grooves 62b constitutean oil reservoir for grease or like other lubricant. The bearing piece62 is disposed within the casings 60, 62 such that the inner aperture62a is engaged with the outer circumferential surface of one end 64a ofthe cylindrical portion 64 and the both end faces of the bearing piece62 are slidably abutted against the lower surface of the disk-likeportion 68 of the casing 61 and the upper surface of the collar portion65 of the casing 60 respectively.

FIG. 23 illustrates an embodiment in which one embodiment of the fifththrust bearing according to the invention as described above is appliedto the strut assembly A.

Specifically, the piston rod 2 of the strut 1 passes through thepenetration aperture 63 of the cylindrical portion 64 of the casing 60and the circular aperture 72 of the disk-like portion 68 of the casing61, the cylindrical portion 64 of the casing 60 is fitted into theaperture of the upper spring seat 8 and the lower surface of the collarportion 65 of the casing 60 is abutted against the flat portion 10 ofthe seat 8, and the upper surface of the disk-like portion 68 of thecasing 61 is abutted against the mounting member 5.

Explanation will be made specifically for one embodiment of a sixththrust bearing according to the present invention referring to FIGS. 24and 25 of the accompanying drawings.

A thrust bearing 20 comprises a lower casing 60 made of synthetic resin,an upper casing 61 made of synthetic resin and a bearing piece 62 madeof synthetic resin disposed within the upper and lower casings 61, 60.

The lower casing 60 includes a cylindrical portion 64 having apenetration aperture 63 being along a longitudinal direction thereof, alarge width collar portion 65 formed integrally with an outercircumferential surface at the end of the cylindrical portion 64 in astate where one end 64a of the cylindrical portion 64 is protrudedtherefrom, an annular protruded portion 66 formed integrally with anouter circumferential edge of the collar portion 65, an engaging portion67 formed to the outer circumferential surface of the protruded portion66 and an annular lower lip 73 formed coaxially with the penetrationaperture 63 at the upper surface of the collar portion 65 and definingan annular groove 74 in cooperation with one end 64a of the cylindricalportion 64.

The engaging portion 67 consists of a tapered surface portion 67a formedfrom an outer circumferential surface of the protruded portion 66 to alower surface of the collar portion 65 and a cylindrical surface portion67b in continuous with the tapered surface portion 67a and reaching thelower surface of the collar portion 65.

The casing 61 includes a disk-like flat portion 68, a circular aperture72 formed at a center of the disk-like portion 68 and having the samediameter as that of the penetration aperture 63, an annular suspendedportion 69 formed integrally with an outer circumferential edge of thedisk-like portion 68, an engaging hook portion 70 formed at a lower endof the suspended portion 69 and an annular upper lip portion 71 formedcoaxially with the circular aperture 72 at a lower surface of thedisk-like portion 68 and having an inner diameter greater than the lowerlip 73 formed to the upper surface of the collar portion 65 of thecasing 60. The hook portion 70 consists of a tapered surface portion 70acorresponding to the tapered surface portion 67a constituting theengaging portion 67 of the casing 60 and a cylindrical surface portion70b in continuous with the tapered surface portion 70a and correspondingto the cylindrical surface portion 67b of the engaging portion 67.

The casing 61 is fitted rotatably to the casing 60 by snap-fitting thehook portion 70 of the suspended portion 69 with the engaging portion 67of the casing 60 and by radially overlapping the end of the upper lipportion 73 with the lower lip portion 71 of the casing 60, whereby tightseals are formed by the labyrinth effect in the snap-fit portion and inthe upper and lower lip portions.

The bearing piece 62 comprises an annular plate having an inner aperture62a of an inner diameter greater than the outer diameter of one end 64aof the cylindrical portion 64 and an outer diameter smaller than theinner diameter of the lower lip portion 73 of the casing 21.

A plurality of grooves 62b are formed radially from the inner aperture62a to the outer circumferential surface alternately on both end facesof the bearing piece 62 at a phase difference of 30 degree with eachother in the circumferential direction, and the grooves 62b constitutean oil reservoir for grease or like other lubricant.

The bearing piece 62 is disposed within the groove 74 of the casing 60such that the inner aperture 62a is engaged with the outercircumferential surface of one end 64a of the cylindrical portion 64,and the both end faces of the bearing piece 62 are slidably abuttedagainst the lower surface of the disk-like portion 68 of the casing 61and the bottom surface of the groove 74 of the casing 60 respectively.

The sliding face of the bearing defined with both end faces of thebearing piece 62, the lower surface of the disk-like portion 68 of thecasing 61 and the bottom face of the groove 74 of the casing 60 abuttedslidably against the both end faces is protected against the intrusionof dust or the like by the labyrinth effect due to tight seals formed inthe snap-fit portion and in the overlapped portions between the upperand lower lip portions 71, 73 of the casings 60, 61.

FIG. 26 illustrates an embodiment in which one embodiment of the sixththrust bearing according to the present invention is applied to a strutassembly A.

Specifically, the piston rod 2 of the strut 1 passes through thepenetration aperture 63 of the cylindrical portion 64 of the casing 60and through the circular aperture 72 of the disk-like portion 68 of thecasing 61, the cylindrical portion 64 of the casing 60 is fitted intothe aperture of the upper spring seat 8, the lower surface of the collarportion 65 of the casing 60 is abutted against the flat portion 10 ofthe seat 8, and the upper surface of the disk-like portion 68 of thecasing 61 is abutted against the mounting member 5.

Explanation will be made specifically for one embodiment of the sevenththrust bearing according to the present invention referring to FIGS. 27and 28 of the accompanying drawings.

A thrust bearing 20 comprises a lower casing 60 made of synthetic resin,an upper casing 61 made of synthetic resin and a bearing piece 62 madeof synthetic resin disposed within the upper and lower casings 61, 60.

The casing 60 includes a cylindrical portion 64 having a penetrationaperture 63 being along a longitudinal direction thereof, an annularfirst lower lip portion 75 disposed to an upper end face of thecylindrical portion 64 and having an aperture of a diameter enlargingwith a step from the penetration aperture 63, a large width collarportion 65 formed integrally with an outer circumferential surface atthe end of the cylindrical portion 64 in a state where one end of thecylindrical portion 64 is protruded therefrom, an annular protrudedportion 66 formed integrally with an outer circumferential edge of thecollar portion 65, an engaging portion 67 formed to an outercircumferential surface of the protruded portion 66 and an annularsecond lower lip portion 76 formed coaxially with the penetrationaperture 63 at an upper surface of the collar portion 65 and defining anannular groove 74 in cooperation with the first lower lip portion 75.The inner diameter of the first lower lip 75 is enlarged than that ofthe penetration aperture 63.

The engaging portion 67 consists of a tapered surface portion 67a formedfrom the outer circumferential surface of the protruded portion 66 tothe lower surface of the collar portion 65 and a cylindrical surfaceportion 67b continuous with the tapered surface portion 67a and reachingthe lower surface of the collar portion 65.

The casing 61 includes a disk-like flat portion 68, a circular aperture72 formed at a center of the disk-like portion 68, an annular firstupper lip 77 formed integrally with and extended downwardly from theinner circumferential edge of the disk-like portion 68 and having anouter diameter smaller than the inner diameter of the first lower lipportion 75, an annular suspended portion 69 formed integrally with theouter circumferential edge of the disk-like portion 68, an engaging hookportion 70 formed at a lower end of the suspended portion 69 and anannular second upper lip portion 78 formed coaxially with the circularaperture 72 to a lower surface of the disk-like portion 68 and having aninner diameter greater than that of the second lower lip portion 76. Thehook portion 70 consists of a tapered surface portion 70a correspondingto the tapered surface portion 67a constituting the engaging portion 67of the casing 60 and a cylindrical surface portion 70b contiguous withthe tapered surface portion 67a and corresponding to the cylindricalsurface 67b of the engaging portion 67.

The casing 61 is fitted rotatably to the lower casing 60 by snap-fittingthe hook portion 70 of the suspended portion 69 with the engagingportion 67 of the casing 60 and by radially overlapping the ends of thefirst upper lip portion 77 and the second upper lip portion 78 with thefirst lower lip portion 75 and the second lower lip portion 76respectively, whereby tight seals are formed by the labyrinth effect inthe snap-fit portion, in the overlapped portion between the first upperand lower lip portions and in the overlapped portion between the secondupper and lower lip portions.

The bearing piece 62 comprises an annular plate having an inner aperture62a of an inner diameter greater than the outer diameter of the firstlower lip portion 75 and an outer diameter smaller than the innerdiameter of the second lower lip portion 76 of the casing 60.

A plurality of grooves 62b are formed radially from the inner aperture62a to the outer circumferential surface alternately on both end facesof the bearing piece 62 at a phase difference of 30 degree with eachother in the circumferential direction, and the grooves 62b constitutean oil reservoir for grease or like other lubricant.

The bearing piece 62 is disposed within the groove 74 of the casing 60such that the inner aperture 62a is engaged with the othercircumferential surface of one end 64a of the cylindrical portion 64,both end faces of the bearing piece 62 are slidably abutted against thelower surface of the disk-like portion 68 of the casing 61 and thebottom face of the groove 74 of the casing 60 respectively.

The sliding face of the bearing defined with the both end faces of thebearing piece 62, the lower surface of the disk-like portion 68 of thecasing 61 and the bottom face of the groove 74 of the casing 60 abuttedslidably against the both end faces is protected against the intrusionof the dust or the like from the inner and the outer circumferentialsurfaces of the bearing piece 62 by the labyrinth effect due to thetight seals formed in the snap-fit portion between the casing 60, 61, inthe overlapped portion between the upper and lower lip portions 77, 75and in the overlapped portion between the second upper and lower lipportions 78, 76 respectively.

FIG. 29 is a longitudinal cross sectional view illustrating anotherembodiment of the seventh thrust bearing according to the presentinvention.

Specifically, in this embodiment, another engaging portion 80 is formedto the inner circumferential surface of the first lower lip portion 75of the casing 60, while another engaging hook portion 81 is formed tothe outer circumferential surface of the upper lip portion 77 at thecentral of the casing 61 in the aforementioned embodiment of the sevenththrust bearing. Both of the engaging portion 80 and the hook portion 81are snap-fit to each other in a relatively rotatably manner.

FIG. 30 illustrates an embodiment in which one embodiment of the sevenththrust bearing according to the present invention is applied to a strutassembly A.

Specifically the piston rod 2 of the strut 1 passes through thepenetration aperture 63 in the cylindrical portion 64 of the casing 60and the circular aperture 72 of the disk-like portion 68 of the casing61, the cylindrical portion 64 of the casing 60 is fitted into theaperture of the upper spring seat 8, the lower surface of the collarportion 65 of the casing 60 is abutted against the flat portion 10 ofthe seat 8, and the upper surface of the disk-like portion 68 of thecasing 61 is abutted against the mounting member 5.

What is claimed is:
 1. A thrust bearing for use with an automobilethrust-strut type suspension having a strut incorporating a shockabsorber, a piston rod inserted in the shock absorber, a mounting memberfor supporting the piston rod to the automobile body, and an upperspring seat loosely engaging the piston rod, the mounting member and theupper spring seat having opposed, substantially planar surfaces offsetfrom each other and defining an annular space between them, said bearingbeing adapted to be received in the annular space between the upperspring seat and the mounting member and adapted to receive the pistonrod therethrough, said bearing comprising:a lower casing made ofsynthetic resin and having a longitudinal axis, said lower casingincluding: a cylindrical portion having a substantially planar uppersurface, a lower surface, an outer circumferential surface, apenetration aperture of circular cross-section coaxial with saidlongitudinal axis of said lower casing, and an annular inner lower lipportion extending upwardly from said upper surface adjacent and offsetstepwise from said penetration aperture, said penetration aperture beingadapted to receive the piston rod of the suspension therein, said innerlower lip defining a cylindrical aperture having a diameter slightlygreater than that of said penetration aperture, and said inner lower lipportion having a distal end offset from said upper surface of saidcylindrical portion; and a collar portion extending outwardly from andformed integrally with said outer circumferential surface of saidcylindrical portion, said collar portion having substantially planarupper and lower surfaces and an outer circumferential surface, saidlower surface of said collar portion being substantially offset fromsaid lower surface of said cylindrical portion and adapted to matinglyengage the upper surface of the upper spring seat of the suspension, andsaid collar portion including an annular protruded portion extendingupwardly from said upper surface of said collar portion and formedintegrally with said outer circumferential surface of said cylindricalportion, said protruded portion having an outer circumferential surfaceand an outwardly extending engaging portion formed on said outercircumferential surface of said protruded portion, and said collarportion further including an annular outer lower lip portion extendingupwardly from said upper surface of said collar portion coaxial withsaid longitudinal axis of said lower casing and defining an innerannular groove in cooperation with said inner lower lip portion and anouter annular groove with said protruded portion, said outer lower lipportion having a distal end offset from said upper surface of saidcollar portion, and said inner annular groove having a bottom surface;said inner annular lower lip having an outer diameter "d1" and saidouter annular lower lip having an inner diameter "d2", respectively,"d1" being smaller than "d2"; an upper casing made of synthetic resinand having a longitudinal axis, said upper casing comprising a disk-likeportion having substantially planar upper and lower surfaces, an outercircumferential edge, a circular aperture formed at the center thereofcoaxial with said longitudinal axis of said upper casing and defining aninner circumferential edge, an annular inner upper lip portion extendingdownwardly from said lower surface of said disk-like portion and formedintegrally with said inner circumferential edge of said disk-likeportion, an annular outer upper lip portion extending downwardly fromsaid lower surface of said disk-like portion coaxial with saidlongitudinal axis of said upper casing, an annular suspended portionextending downwardly from said lower surface of said disk-like portionand forged integrally with said outer circumferential edge of saiddisk-like portion, said upper surface of said disk-like portion beingadapted to matingly engage the lower surface of the mounting member ofthe suspension, said circular aperture being adapted to receive thepiston rod of the suspension therein, said inner and outer upper annularlip portions each having a distal end offset from said lower surface ofsaid disk-like portion, and said suspended portion having a distal endoffset from said lower surface of said disk-like portion and an engaginghook portion formed at said distal end for cooperation with saidengaging portion of said protruded portion; and a bearing piece made ofsynthetic resin and comprising an annular plate having upper and lowersurfaces and an inner diameter greater than "d1" and an outer diameterless that "d2", said bearing piece being received in said inner annulargroove of said lower casing; said hook portion of said suspended portionof said upper casing being snap-fitted with said engaging portion ofsaid protruded portion of said lower casing to define a snap-fitportion, whereby said upper casing is fitted rotatably to said lowercasing, said upper surface of said bearing piece being slidably abuttedagainst said lower surface of said disk-like portion, said distal endsof said inner and outer upper lip portions being overlapped radiallywith said distal ends of said inner and outer lower lip portions,respectively, to define inner and outer overlapped portions,respectively, and said lower surface of said bearing piece beingslidably abutted against said bottom surface of said inner annulargroove, whereby tight seals are formed at said snap-fit portion and saidinner and outer overlapped portions.
 2. The bearing as claimed in claim1, said inner upper lip portion having an engaging hook portion formedat said distal end thereof and said inner lower lip portion having anengaging portion formed at said distal end thereof for cooperation withsaid hook portion of said inner upper lip portion, said hook portion ofsaid inner upper lip portion being snap-fitted and relatively rotatablyengaged with said engaging portion of said inner lower lip portion. 3.The bearing as claimed in claim 1, said bearing piece having an outercircumferential surface and a plurality of grooves in said upper andlower surfaces thereof extending radially from said inner aperture tosaid outer circumferential surface, said grooves being in said upper andlower surfaces alternately at a phase difference of approximately 30degrees with each other in a circumferential direction.